This invention concerns improvements in and relating to film of aromatic polyamides such as poly-meta-phenylene isophthalamide, and to a process for making the improved film.
Film of an aromatic polyamide is known in the art, such as disclosed in U.S. Pat. Nos. 3,287,324 and 4,070,433, and is desirable for various uses in view of its low flammability. However, as initially prepared, noncrystalline and undrawn film is unsuitable for some uses because of generally inadequate values of certain physical properties indicative of toughness, such as its physical strength as evidenced, for example, by pneumatic impact strength and by resistance to breakage in a wire bend test to be described below. Although crystalline film retains good tenacity and elongation at high temperature, it tends to be brittle. Drawn film tends to have better physical strength, but is expensive to make because of the cost of the apparatus and process used for drawing.
It is therefore an object of this invention to provide film of aromatic polyamide which is noncrystalline and undrawn, and yet has toughness.
It is a further object to provide a process for making such film.